99 Regal GS Fuel Tank Pressure/Gas Coming Out When Filling Up!!

[stlzed1]

GREAT site, just joined. I have a 99 Regal GS supercharged, 3.8, 110,000 miles, runs great. BUT, recently about 2 weeks ago the SERVICE ENGINE SOON light came on. Don't have a code reader, took to AutoZone, they said something with fuel cap or vaccuum leak (?) in fuel system. They reset light, 2 days later it was back on. When I put gas in it, when putting the fuel hose nozzle into the tank, past the little flap in the filler neck, there's pressure in there you can hear escaping when the flap is pushed in. And, a few times, the pressure was so great that the gas actually wouldn't go into the tank when I started fiilling, it actually came back out the filler neck even though tank was nearly empty. I waited a few seconds for the pressure to go down and then was able to fill it up. But do you have any ideas what could cause that - buildup of pressure in fuel system or tank accompanied by SERVICE ENGINE SOON light? Any/all info appreciated!! Thanks!

[HotZ28]

Welcome to AF! Apparently, you have an EVAP system problem. It is important to remember the DTC’s (codes) so you will know where to start troubleshooting. Evaporative emissions system problems fall into three basic categories: component and circuit DTCs, purge flow DTCs and leak detection DTCs. The type of code present, will determine the diagnostic path.

[BNaylor]

Best thing to do is get and post the diagnostic trouble codes (DTC). It sounds like a purge cycle issue. Although it depends on the DTC, one common or overlooked cause is the evaporative emissions charcoal cannister being saturated with gasoline not allowing the gas tank vapors to get back to the intake system.